﻿/**************************************************************************\
    Copyright Microsoft Corporation. All Rights Reserved.
\**************************************************************************/

namespace WindowChromeFix
{
    using System;
    using System.Collections.Generic;
    using System.Diagnostics.CodeAnalysis;
    using System.Runtime.InteropServices;
    using System.Security;
    using System.Security.Permissions;
    using System.Windows;
    using System.Windows.Interop;
    using System.Windows.Media;
    using System.Windows.Threading;
    using Standard;
    using System.Reflection;
    
    using HANDLE_MESSAGE = KeyValuePair<Standard.WM, Standard.MessageHandler>;

    internal class WindowChromeWorkerFix : DependencyObject
    {
        // Delegate signature used for Dispatcher.BeginInvoke.
        private delegate void _Action();

        #region Fields

        private const SWP _SwpFlags = SWP.FRAMECHANGED | SWP.NOSIZE | SWP.NOMOVE | SWP.NOZORDER | SWP.NOOWNERZORDER | SWP.NOACTIVATE;

        private readonly List<HANDLE_MESSAGE> _messageTable;

        /// <summary>The Window that's chromeFix is being modified.</summary>
        private Window _window;

        /// <summary>Underlying HWND for the _window.</summary>
        /// <SecurityNote>
        ///   Critical : Critical member
        /// <SecurityNote>
        [SecurityCritical]
        private IntPtr _hwnd;

        /// <summary>Underlying HWND for the _window.</summary>
        /// <SecurityNote>
        ///   Critical : Critical member provides access to HWND's window messages which are critical
        /// <SecurityNote>
        [SecurityCritical]
        private HwndSource _hwndSource = null;

        private bool _isHooked = false;

        // These fields are for tracking workarounds for WPF 3.5SP1 behaviors.
        private bool _isFixedUp = false;
        private bool _isUserResizing = false;
        private bool _hasUserMovedWindow = false;
        private Point _windowPosAtStartOfUserMove = default(Point);

        /// <summary>Object that describes the current modifications being made to the chromeFix.</summary>
        private WindowChromeFix ChromeFixInfo;

        // Keep track of this so we can detect when we need to apply changes.  Tracking these separately
        // as I've seen using just one cause things to get enough out of sync that occasionally the caption will redraw.
        private WindowState _lastRoundingState;
        private WindowState _lastMenuState;
        private bool _isGlassEnabled;

        #endregion

        /// <SecurityNote>
        ///   Critical : Initializes critical members
        /// <SecurityNote>
        [SecurityCritical]
        static WindowChromeWorkerFix()
        {
            var type = typeof(Window);
            VisualChildrenChangedEventInfo = type.GetEvent("VisualChildrenChanged")!;
            GetDpiMethodInfo = type.GetMethod("GetDpi", BindingFlags.NonPublic | BindingFlags.Instance)!;
        }

        private static EventInfo VisualChildrenChangedEventInfo;
        private static MethodInfo GetDpiMethodInfo;

        private static void ListenVisualChildrenChangedEvent(Window window, EventHandler handler)
        {
            VisualChildrenChangedEventInfo.AddEventHandler(window, handler);
        }
        
        private static void RemoveVisualChildrenChangedEvent(Window window, EventHandler handler)
        {
            VisualChildrenChangedEventInfo.RemoveEventHandler(window, handler);
        }
        
        private static DpiScale GetDpi(Window window)
        {
            return (DpiScale)GetDpiMethodInfo.Invoke(window, null)!;
        }
        

        /// <SecurityNote>
        ///   Critical : Store critical methods in critical callback table
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        public WindowChromeWorkerFix()
        {
            _messageTable = new List<HANDLE_MESSAGE>
            {
                // new HANDLE_MESSAGE(WM.SETTEXT,               _HandleSetTextOrIcon),
                // new HANDLE_MESSAGE(WM.SETICON,               _HandleSetTextOrIcon),
                // new HANDLE_MESSAGE(WM.NCACTIVATE,            _HandleNCActivate),
                new HANDLE_MESSAGE(WM.NCCALCSIZE,            _HandleNCCalcSize),
                new HANDLE_MESSAGE(WM.NCHITTEST,             _HandleNCHitTest),
                // new HANDLE_MESSAGE(WM.NCRBUTTONUP,           _HandleNCRButtonUp),
                // new HANDLE_MESSAGE(WM.SIZE,                  _HandleSize),
                // new HANDLE_MESSAGE(WM.WINDOWPOSCHANGED,      _HandleWindowPosChanged),
                // new HANDLE_MESSAGE(WM.DWMCOMPOSITIONCHANGED, _HandleDwmCompositionChanged),
            };
            
            if (Utility.IsPresentationFrameworkVersionLessThan4)
            {
                // _messageTable.AddRange(new[]
                // {
                //    new HANDLE_MESSAGE(WM.SETTINGCHANGE,         _HandleSettingChange),
                //    new HANDLE_MESSAGE(WM.ENTERSIZEMOVE,         _HandleEnterSizeMove),
                //    new HANDLE_MESSAGE(WM.EXITSIZEMOVE,          _HandleExitSizeMove),
                //    new HANDLE_MESSAGE(WM.MOVE,                  _HandleMove),
                // });
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        public void SetWindowChrome(WindowChromeFix newChromeFix)
        {
            VerifyAccess();
            Assert.IsNotNull(_window);

            if (newChromeFix == ChromeFixInfo)
            {
                // Nothing's changed.
                return;
            }

            if (ChromeFixInfo != null)
            {
                ChromeFixInfo.PropertyChangedThatRequiresRepaint -= OnChromeFixPropertyChangedThatRequiresRepaint;
            }

            ChromeFixInfo = newChromeFix;
            if (ChromeFixInfo != null)
            {
                ChromeFixInfo.PropertyChangedThatRequiresRepaint += OnChromeFixPropertyChangedThatRequiresRepaint;
            }

            // _ApplyNewCustomChrome();
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private void OnChromeFixPropertyChangedThatRequiresRepaint(object sender, EventArgs e)
        {
            _UpdateFrameState(true);
        }

        public static readonly DependencyProperty WindowChromeWorkerProperty = DependencyProperty.RegisterAttached(
            "WindowChromeWorkerFix",
            typeof(WindowChromeWorkerFix),
            typeof(WindowChromeWorkerFix),
            new PropertyMetadata(null, _OnChromeWorkerChanged));

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private static void _OnChromeWorkerChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            var w = (Window)d;
            var cw = (WindowChromeWorkerFix)e.NewValue;

            // The WindowChromeWorkerFix object should only be set on the window once, and never to null.
            Assert.IsNotNull(w);
            Assert.IsNotNull(cw);
            Assert.IsNull(cw._window);

            cw._SetWindow(w);
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _SetWindow(Window window)
        {
            Assert.IsNull(_window);
            Assert.IsNotNull(window);

            UnsubscribeWindowEvents();

            _window = window;

            // There are potentially a couple funny states here.
            // The window may have been shown and closed, in which case it's no longer usable.
            // We shouldn't add any hooks in that case, just exit early.
            // If the window hasn't yet been shown, then we need to make sure to remove hooks after it's closed.
            _hwnd = new WindowInteropHelper(_window).Handle;

            // On older versions of the framework the client size of the window is incorrectly calculated.
            // We need to modify the template to fix this on behalf of the user.
            Utility.AddDependencyPropertyChangeListener(_window, Window.TemplateProperty, _OnWindowPropertyChangedThatRequiresTemplateFixup);
            Utility.AddDependencyPropertyChangeListener(_window, Window.FlowDirectionProperty, _OnWindowPropertyChangedThatRequiresTemplateFixup);

            _window.Closed += _UnsetWindow;

            // Use whether we can get an HWND to determine if the Window has been loaded.
            if (IntPtr.Zero != _hwnd)
            {
                // We've seen that the HwndSource can't always be retrieved from the HWND, so cache it early.
                // Specifically it seems to sometimes disappear when the OS theme is changing.
                _hwndSource = HwndSource.FromHwnd(_hwnd);
                Assert.IsNotNull(_hwndSource);
                _window.ApplyTemplate();

                if (ChromeFixInfo != null)
                {
                    _ApplyNewCustomChrome();
                }
            }
            else
            {
                _window.SourceInitialized += _WindowSourceInitialized;
            }
        }

        /// <SecurityNote>
        ///   Critical : Store critical methods in critical callback table
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private void _WindowSourceInitialized(object sender, EventArgs e)
        {
            _hwnd = new WindowInteropHelper(_window).Handle;
            Assert.IsNotDefault(_hwnd);
            _hwndSource = HwndSource.FromHwnd(_hwnd);
            Assert.IsNotNull(_hwndSource);

            if (ChromeFixInfo != null)
            {
                _ApplyNewCustomChrome();
            }
        }

        /// <SecurityNote>
        ///   Critical : References critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void UnsubscribeWindowEvents()
        {
            if (_window != null)
            {
                Utility.RemoveDependencyPropertyChangeListener(_window, Window.TemplateProperty, _OnWindowPropertyChangedThatRequiresTemplateFixup);
                Utility.RemoveDependencyPropertyChangeListener(_window, Window.FlowDirectionProperty, _OnWindowPropertyChangedThatRequiresTemplateFixup);
                _window.SourceInitialized -= _WindowSourceInitialized;
                _window.StateChanged -= _FixupRestoreBounds;
            }
        }

        /// <SecurityNote>
        ///   Critical : Store critical methods in critical callback table
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private void _UnsetWindow(object sender, EventArgs e)
        {
            UnsubscribeWindowEvents();

            if (ChromeFixInfo != null)
            {
                ChromeFixInfo.PropertyChangedThatRequiresRepaint -= OnChromeFixPropertyChangedThatRequiresRepaint;
            }

            _RestoreStandardChromeState(true);
        }

        [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")]
        public static WindowChromeWorkerFix GetWindowChromeWorker(Window window)
        {
            Verify.IsNotNull(window, "window");
            return (WindowChromeWorkerFix)window.GetValue(WindowChromeWorkerProperty);
        }

        [SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters")]
        public static void SetWindowChromeWorker(Window window, WindowChromeWorkerFix chrome)
        {
            Verify.IsNotNull(window, "window");
            window.SetValue(WindowChromeWorkerProperty, chrome);
        }

        /// <SecurityNote>
        ///   Critical : Accesses critical _hwnd field
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private void _OnWindowPropertyChangedThatRequiresTemplateFixup(object sender, EventArgs e)
        {
            if (ChromeFixInfo != null && _hwnd != IntPtr.Zero)
            {
                // Assume that when the template changes it's going to be applied.
                // We don't have a good way to externally hook into the template
                // actually being applied, so we asynchronously post the fixup operation
                // at Loaded priority, so it's expected that the visual tree will be
                // updated before _FixupTemplateIssues is called.
                // 
                // Also see comments in RetryFixupTemplateIssuesOnVisualChildrenAdded which is another
                // place where _FixupTemplateIssues is posted. 
                _window.Dispatcher.BeginInvoke(DispatcherPriority.Loaded, (_Action)_FixupTemplateIssues);
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _ApplyNewCustomChrome()
        {
            if (_hwnd == IntPtr.Zero || _hwndSource.IsDisposed)
            {
                // Not yet hooked.
                return;
            }

            if (ChromeFixInfo == null)
            {
                _RestoreStandardChromeState(false);
                return;
            }

            if (!_isHooked)
            {
                _hwndSource.AddHook(_WndProc);
                _isHooked = true;
            }

            _FixupTemplateIssues();

            // Force this the first time.
            _UpdateSystemMenu(_window.WindowState);
            _UpdateFrameState(true);
            
            NativeMethods.SetWindowPos(_hwnd, IntPtr.Zero, 0, 0, 0, 0, _SwpFlags);
        }

        /// <summary>
        /// If visual children have been added to <see cref="_window"/>, then repost <see cref="_FixupTemplateIssues"/>
        /// </summary>
        /// <SecurityNote>
        ///   Critical : Accesses Critical method <see cref="_FixupTemplateIssues"/>
        ///   Safe     : Does not return or expose Critical resources to the caller
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
        private void RetryFixupTemplateIssuesOnVisualChildrenAdded(object? sender, EventArgs e)
        {
            if (sender == _window)
            {
                // Remove the handler for Window.VisualChildrenChanged. This will be hooked up 
                // again in _FixupTemplatedIssues if needed

                RemoveVisualChildrenChangedEvent(_window, RetryFixupTemplateIssuesOnVisualChildrenAdded);
                // _window.VisualChildrenChanged -= RetryFixupTemplateIssuesOnVisualChildrenAdded;

                // At this point, the Window and the its root element are ready. Repost _FixupTemplateIssues
                // at Render priority to ensure that it gets the root element fixed up ASAP. 
                // 
                // Also see comments in _OnWindowPropertyChangedThatRequiresTemplateFixup which is another
                // place where _FixupTemplateIssues is posted. 
                _window.Dispatcher.BeginInvoke(DispatcherPriority.Render, (_Action)_FixupTemplateIssues);
            }
        }

        
        
        
        
        
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _FixupTemplateIssues()
        {
            Assert.IsNotNull(ChromeFixInfo);
            Assert.IsNotNull(_window);

            if (_window.Template == null)
            {
                // Nothing to fixup yet.  This will get called again when a template does get set.
                return;
            }

            // Guard against the visual tree being empty.
            if (VisualTreeHelper.GetChildrenCount(_window) == 0)
            {
                // The template isn't null, but we don't have a visual tree.
                // Wait for the visual tree after ApplyTemplate, and then repost this  
                // _window.VisualChildrenChanged += RetryFixupTemplateIssuesOnVisualChildrenAdded;
                ListenVisualChildrenChangedEvent(_window, RetryFixupTemplateIssuesOnVisualChildrenAdded);
                return;
            }

            Thickness templateFixupMargin = default(Thickness);
            Transform templateFixupTransform = null;

            var rootElement = (FrameworkElement)VisualTreeHelper.GetChild(_window, 0);

            if (ChromeFixInfo.NonClientFrameEdges != NonClientFrameEdges.None)
            {
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Top))
                {
                    templateFixupMargin.Top -= SystemParameters.WindowResizeBorderThickness.Top;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Left))
                {
                     templateFixupMargin.Left -= SystemParameters.WindowResizeBorderThickness.Left;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Bottom))
                {
                    templateFixupMargin.Bottom -= SystemParameters.WindowResizeBorderThickness.Bottom;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Right))
                {
                    templateFixupMargin.Right -= SystemParameters.WindowResizeBorderThickness.Right;
                }
            }

            if (Utility.IsPresentationFrameworkVersionLessThan4)
            {
                // DpiScale dpi = _window.GetDpi();
                DpiScale dpi = GetDpi(_window);
                RECT rcWindow = NativeMethods.GetWindowRect(_hwnd);
                RECT rcAdjustedClient = _GetAdjustedWindowRect(rcWindow);

                Rect rcLogicalWindow = DpiHelper.DeviceRectToLogical(new Rect(rcWindow.Left, rcWindow.Top, rcWindow.Width, rcWindow.Height), dpi.DpiScaleX, dpi.DpiScaleY);
                Rect rcLogicalClient = DpiHelper.DeviceRectToLogical(new Rect(rcAdjustedClient.Left, rcAdjustedClient.Top, rcAdjustedClient.Width, rcAdjustedClient.Height), dpi.DpiScaleX, dpi.DpiScaleY);

                if (!Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Left))
                {
                    templateFixupMargin.Right -= SystemParameters.WindowResizeBorderThickness.Left;
                }

                if (!Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Right))
                {
                    templateFixupMargin.Right -= SystemParameters.WindowResizeBorderThickness.Right;
                }

                if (!Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Top))
                {
                    templateFixupMargin.Bottom -= SystemParameters.WindowResizeBorderThickness.Top;
                }

                if (!Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Bottom))
                {
                    templateFixupMargin.Bottom -= SystemParameters.WindowResizeBorderThickness.Bottom;
                }

                templateFixupMargin.Bottom -= SystemParameters.WindowCaptionHeight;


                // The negative thickness on the margin doesn't properly get applied in RTL layouts.
                // The width is right, but there is a black bar on the right.
                // To fix this we just add an additional RenderTransform to the root element.
                // This works fine, but if the window is dynamically changing its FlowDirection then this can have really bizarre side effects.
                // This will mostly work if the FlowDirection is dynamically changed, but there aren't many real scenarios that would call for
                // that so I'm not addressing the rest of the quirkiness.
                if (_window.FlowDirection == FlowDirection.RightToLeft)
                {
                    Thickness nonClientThickness = new Thickness(
                       rcLogicalWindow.Left - rcLogicalClient.Left,
                       rcLogicalWindow.Top - rcLogicalClient.Top,
                       rcLogicalClient.Right - rcLogicalWindow.Right,
                       rcLogicalClient.Bottom - rcLogicalWindow.Bottom);

                    templateFixupTransform = new MatrixTransform(1, 0, 0, 1, -(nonClientThickness.Left + nonClientThickness.Right), 0);
                }
                else
                {
                    templateFixupTransform = null;
                }

                rootElement.RenderTransform = templateFixupTransform;
            }

            rootElement.Margin = templateFixupMargin;

            if (Utility.IsPresentationFrameworkVersionLessThan4)
            {
                if (!_isFixedUp)
                {
                    _hasUserMovedWindow = false;
                    _window.StateChanged += _FixupRestoreBounds;

                    _isFixedUp = true;
                }
            }
        }

        /// <SecurityNote>
        ///   Critical : Store critical methods in critical callback table
        ///   Safe     : Demands full trust permissions
        /// <SecurityNote>
        [SecuritySafeCritical]
        [PermissionSet(SecurityAction.Demand, Name="FullTrust")]
        private void _FixupRestoreBounds(object sender, EventArgs e)
        {
            Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
            if (_window.WindowState == WindowState.Maximized || _window.WindowState == WindowState.Minimized)
            {
                // Old versions of WPF sometimes force their incorrect idea of the Window's location
                // on the Win32 restore bounds.  If we have reason to think this is the case, then
                // try to undo what WPF did after it has done its thing.
                if (_hasUserMovedWindow)
                {
                    // DpiScale dpi = _window.GetDpi();
                    DpiScale dpi =  GetDpi(_window);
                    _hasUserMovedWindow = false;
                    WINDOWPLACEMENT wp = NativeMethods.GetWindowPlacement(_hwnd);

                    RECT adjustedDeviceRc = _GetAdjustedWindowRect(new RECT { Bottom = 100, Right = 100 });
                    Point adjustedTopLeft = DpiHelper.DevicePixelsToLogical(
                        new Point(
                            wp.rcNormalPosition.Left - adjustedDeviceRc.Left,
                            wp.rcNormalPosition.Top - adjustedDeviceRc.Top),
                        dpi.DpiScaleX,
                        dpi.DpiScaleY);

                    _window.Top = adjustedTopLeft.Y;
                    _window.Left = adjustedTopLeft.X;
                }
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private RECT _GetAdjustedWindowRect(RECT rcWindow)
        {
            // This should only be used to work around issues in the Framework that were fixed in 4.0
            Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);

            var style = (WS)NativeMethods.GetWindowLongPtr(_hwnd, GWL.STYLE);
            var exstyle = (WS_EX)NativeMethods.GetWindowLongPtr(_hwnd, GWL.EXSTYLE);

            return NativeMethods.AdjustWindowRectEx(rcWindow, style, false, exstyle);
        }

        // // Windows tries hard to hide this state from applications.
        // // Generally you can tell that the window is in a docked position because the restore bounds from GetWindowPlacement
        // // don't match the current window location and it's not in a maximized or minimized state.
        // // Because this isn't doced or supported, it's also not incredibly consistent.  Sometimes some things get updated in
        // // different orders, so this isn't absolutely reliable.
        // /// <SecurityNote>
        // ///   Critical : Calls critical method
        // /// <SecurityNote>
        // private bool _IsWindowDocked
        // {
        //     [SecurityCritical]
        //     get
        //     {
        //         // We're only detecting this state to work around .Net 3.5 issues.
        //         // This logic won't work correctly when those issues are fixed.
        //         Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
        //
        //         if (_window.WindowState != WindowState.Normal)
        //         {
        //             return false;
        //         }
        //
        //         // DpiScale dpi = _window.GetDpi();
        //         DpiScale dpi =  GetDpi(_window);
        //
        //         RECT adjustedOffset = _GetAdjustedWindowRect(new RECT { Bottom = 100, Right = 100 });
        //         Point windowTopLeft = new Point(_window.Left, _window.Top);
        //         windowTopLeft -= (Vector)DpiHelper.DevicePixelsToLogical(new Point(adjustedOffset.Left, adjustedOffset.Top), dpi.DpiScaleX, dpi.DpiScaleY);
        //
        //         return _window.RestoreBounds.Location != windowTopLeft;
        //     }
        // }

        #region WindowProc and Message Handlers

        /// <SecurityNote>
        ///   Critical : Accesses critical _hwnd
        /// <SecurityNote>
        [SecurityCritical]
        private IntPtr _WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            // Only expecting messages for our cached HWND.
            Assert.AreEqual(hwnd, _hwnd);

            var message = (WM)msg;
            foreach (var handlePair in _messageTable)
            {
                if (handlePair.Key == message)
                {
                    return handlePair.Value(message, wParam, lParam, out handled);
                }
            }
            return IntPtr.Zero;
        }
        
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleSetTextOrIcon(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     bool modified = _ModifyStyle(WS.VISIBLE, 0);
        //
        //     // Setting the caption text and icon cause Windows to redraw the caption.
        //     // Letting the default WndProc handle the message without the WS_VISIBLE
        //     // style applied bypasses the redraw.
        //     IntPtr lRet = NativeMethods.DefWindowProc(_hwnd, uMsg, wParam, lParam);
        //
        //     // Put back the style we removed.
        //     if (modified)
        //     {
        //         _ModifyStyle(0, WS.VISIBLE);
        //     }
        //     handled = true;
        //     return lRet;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleNCActivate(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // Despite MSDN's documentation of lParam not being used,
        //     // calling DefWindowProc with lParam set to -1 causes Windows not to draw over the caption.
        //
        //     // Directly call DefWindowProc with a custom parameter
        //     // which bypasses any other handling of the message.
        //     IntPtr lRet = NativeMethods.DefWindowProc(_hwnd, WM.NCACTIVATE, wParam, new IntPtr(-1));
        //     handled = true;
        //     return lRet;
        // }
        //
        // Black Border Workaround
        //
        // 762437 - DWM: Windows that have both clip and alpha margins are drawn without respecting alpha
        // There was a regression in DWM in Windows 7 with regard to handling WM_NCCALCSIZE to effect custom chromeFix.
        // When windows with glass are maximized on a multi-monitor setup, the glass frame tends to turn black.
        // Also, when windows are resized they tend to flicker black, sometimes staying that way until resized again.
        //
        // At least on RTM Win7 we can avoid the problem by making the client area not extactly match the non-client
        // area, so we added the NonClientFrameEdges property.
        /// <SecurityNote>
        ///   Critical : Calls critical Marshal.PtrToStructure
        /// <SecurityNote>
        [SecurityCritical]
        private IntPtr _HandleNCCalcSize(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        {
            // lParam is an [in, out] that can be either a RECT* (wParam == FALSE) or an NCCALCSIZE_PARAMS*.
            // Since the first field of NCCALCSIZE_PARAMS is a RECT and is the only field we care about
            // we can unconditionally treat it as a RECT.
        
            if (ChromeFixInfo.NonClientFrameEdges != NonClientFrameEdges.None)
            {
                // DpiScale dpi = _window.GetDpi();
                DpiScale dpi =  GetDpi(_window);
                Thickness windowResizeBorderThicknessDevice = DpiHelper.LogicalThicknessToDevice(SystemParameters.WindowResizeBorderThickness, dpi.DpiScaleX, dpi.DpiScaleY);
            
                var rcClientArea = (RECT)Marshal.PtrToStructure(lParam, typeof(RECT));
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Top))
                {
                    rcClientArea.Top += (int)windowResizeBorderThicknessDevice.Top;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Left))
                {
                    rcClientArea.Left += (int)windowResizeBorderThicknessDevice.Left;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Bottom))
                {
                    rcClientArea.Bottom -= (int)windowResizeBorderThicknessDevice.Bottom;
                }
                if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Right))
                {
                    rcClientArea.Right -= (int)windowResizeBorderThicknessDevice.Right;
                }
            
                Marshal.StructureToPtr(rcClientArea, lParam, false);
            }
        
            handled = true;
        
            // Per MSDN for NCCALCSIZE, always return 0 when wParam == FALSE
            // 
            // Returning 0 when wParam == TRUE is not appropriate - it will preserve
            // the old client area and align it with the upper-left corner of the new 
            // client area. So we simply ask for a redraw (WVR_REDRAW)
        
            IntPtr retVal = IntPtr.Zero;
            if (wParam.ToInt32() != 0) // wParam == TRUE
            {
                retVal = new IntPtr((int) (WVR.REDRAW));
            }
        
            return retVal; 
        }
        
        private HT _GetHTFromResizeGripDirection(ResizeGripDirection direction)
        {
            bool compliment = _window.FlowDirection == FlowDirection.RightToLeft;
            switch (direction)
            {
                case ResizeGripDirection.Bottom:
                    return HT.BOTTOM;
                case ResizeGripDirection.BottomLeft:
                    return compliment ? HT.BOTTOMRIGHT : HT.BOTTOMLEFT;
                case ResizeGripDirection.BottomRight:
                    return compliment ? HT.BOTTOMLEFT : HT.BOTTOMRIGHT;
                case ResizeGripDirection.Left:
                    return compliment ? HT.RIGHT : HT.LEFT;
                case ResizeGripDirection.Right:
                    return compliment ? HT.LEFT : HT.RIGHT;
                case ResizeGripDirection.Top:
                    return HT.TOP;
                case ResizeGripDirection.TopLeft:
                    return compliment ? HT.TOPRIGHT : HT.TOPLEFT;
                case ResizeGripDirection.TopRight:
                    return compliment ? HT.TOPLEFT : HT.TOPRIGHT;
                default:
                    return HT.NOWHERE;
            }
        }
        
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private IntPtr _HandleNCHitTest(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        {
            // DpiScale dpi = _window.GetDpi();
            DpiScale dpi =  GetDpi(_window);
        
            // Let the system know if we consider the mouse to be in our effective non-client area.
            var mousePosScreen = new Point(Utility.GET_X_LPARAM(lParam), Utility.GET_Y_LPARAM(lParam));
            Rect windowPosition = _GetWindowRect();
        
            Point mousePosWindow = mousePosScreen;
            mousePosWindow.Offset(-windowPosition.X, -windowPosition.Y);
            mousePosWindow = DpiHelper.DevicePixelsToLogical(mousePosWindow, dpi.DpiScaleX, dpi.DpiScaleY);
        
            // If the app is asking for content to be treated as client then that takes precedence over _everything_, even DWM caption buttons.
            // This allows apps to set the glass frame to be non-empty, still cover it with WPF content to hide all the glass,
            // yet still get DWM to draw a drop shadow.
            IInputElement inputElement = _window.InputHitTest(mousePosWindow);
            if (inputElement != null)
            {
                if (WindowChromeFix.GetIsHitTestVisibleInChrome(inputElement))
                {
                    handled = true;
                    return new IntPtr((int)HT.CLIENT);
                }
        
                ResizeGripDirection direction = WindowChromeFix.GetResizeGripDirection(inputElement);
                if (direction != ResizeGripDirection.None)
                {
                    handled = true;
                    return new IntPtr((int)_GetHTFromResizeGripDirection(direction));
                }
            }
        
            // It's not opted out, so offer up the hittest to DWM, then to our custom non-client area logic.
            if (ChromeFixInfo.UseAeroCaptionButtons)
            {
                IntPtr lRet;
                if (Utility.IsOSVistaOrNewer && ChromeFixInfo.GlassFrameThickness != default(Thickness) && _isGlassEnabled)
                {
                    // If we're on Vista, give the DWM a chance to handle the message first.
                    handled = NativeMethods.DwmDefWindowProc(_hwnd, uMsg, wParam, lParam, out lRet);
        
                    if (IntPtr.Zero != lRet)
                    {
                        // If DWM claims to have handled this, then respect their call.
                        return lRet;
                    }
                }
            }
        
            HT ht = _HitTestNca(
                DpiHelper.DeviceRectToLogical(windowPosition, dpi.DpiScaleX, dpi.DpiScaleY),
                DpiHelper.DevicePixelsToLogical(mousePosScreen, dpi.DpiScaleX, dpi.DpiScaleY));
        
            handled = true;
            return new IntPtr((int)ht);
        }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical method
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleNCRButtonUp(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // Emulate the system behavior of clicking the right mouse button over the caption area
        //     // to bring up the system menu.
        //     if (HT.CAPTION == (HT)wParam.ToInt32())
        //     {
        //         // SystemCommands.ShowSystemMenuPhysicalCoordinates(_window, new Point(Utility.GET_X_LPARAM(lParam), Utility.GET_Y_LPARAM(lParam)));
        //         ShowSystemMenuPhysicalCoordinates(_window, new Point(Utility.GET_X_LPARAM(lParam), Utility.GET_Y_LPARAM(lParam)));
        //     }
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // internal static void ShowSystemMenuPhysicalCoordinates(Window window, Point physicalScreenLocation)
        // {
        //     const uint TPM_RETURNCMD = 0x0100;
        //     const uint TPM_LEFTBUTTON = 0x0;
        //
        //     Verify.IsNotNull(window, "window");
        //     IntPtr hwnd = new WindowInteropHelper(window).Handle;
        //     if (hwnd == IntPtr.Zero || !NativeMethods.IsWindow(hwnd))
        //     {
        //         return;
        //     }
        //
        //     IntPtr hmenu = NativeMethods.GetSystemMenu(hwnd, false);
        //
        //     uint cmd = NativeMethods.TrackPopupMenuEx(hmenu, TPM_LEFTBUTTON | TPM_RETURNCMD, (int)physicalScreenLocation.X, (int)physicalScreenLocation.Y, hwnd, IntPtr.Zero);
        //     if (0 != cmd)
        //     {
        //         NativeMethods.PostMessage(hwnd, WM.SYSCOMMAND, new IntPtr(cmd), IntPtr.Zero);
        //     }
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical method
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleSize(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     const int SIZE_MAXIMIZED = 2;
        //
        //     // Force when maximized.
        //     // We can tell what's happening right now, but the Window doesn't yet know it's
        //     // maximized.  Not forcing this update will eventually cause the
        //     // default caption to be drawn.
        //     WindowState? state = null;
        //     if (wParam.ToInt32() == SIZE_MAXIMIZED)
        //     {
        //         state = WindowState.Maximized;
        //     }
        //     _UpdateSystemMenu(state);
        //
        //     // Still let the default WndProc handle this.
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical Marshal.PtrToStructure
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleWindowPosChanged(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // http://blogs.msdn.com/oldnewthing/archive/2008/01/15/7113860.aspx
        //     // The WM_WINDOWPOSCHANGED message is sent at the end of the window
        //     // state change process. It sort of combines the other state change
        //     // notifications, WM_MOVE, WM_SIZE, and WM_SHOWWINDOW. But it doesn't
        //     // suffer from the same limitations as WM_SHOWWINDOW, so you can
        //     // reliably use it to react to the window being shown or hidden.
        //
        //     Assert.IsNotDefault(lParam);
        //     var wp = (WINDOWPOS)Marshal.PtrToStructure(lParam, typeof(WINDOWPOS));
        //
        //     // We only care to take action when the window dimensions are changing.
        //     // Otherwise, we may get a StackOverflowException.  See Dev11 49900.
        //     if (!Utility.IsFlagSet(wp.flags, (int)SWP.NOSIZE))
        //     {
        //         _UpdateSystemMenu(null);
        //
        //         if (!_isGlassEnabled)
        //         {
        //             _SetRoundingRegion(wp);
        //         }
        //     }
        //
        //     // Still want to pass this to DefWndProc
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleDwmCompositionChanged(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     _UpdateFrameState(false);
        //
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleSettingChange(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // There are several settings that can cause fixups for the template to become invalid when changed.
        //     // These shouldn't be required on the v4 framework.
        //     Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
        //
        //     _FixupTemplateIssues();
        //
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // /// <SecurityNote>
        // ///   Critical : Calls critical methods
        // /// <SecurityNote>
        // [SecurityCritical]
        // private IntPtr _HandleEnterSizeMove(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // This is only intercepted to deal with bugs in Window in .Net 3.5 and below.
        //     Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
        //
        //     _isUserResizing = true;
        //
        //     // On Win7 if the user is dragging the window out of the maximized state then we don't want to use that location
        //     // as a restore point.
        //     Assert.Implies(_window.WindowState == WindowState.Maximized, Utility.IsOSWindows7OrNewer);
        //     if (_window.WindowState != WindowState.Maximized)
        //     {
        //         // Check for the docked window case.  The window can still be restored when it's in this position so
        //         // try to account for that and not update the start position.
        //         if (!_IsWindowDocked)
        //         {
        //             _windowPosAtStartOfUserMove = new Point(_window.Left, _window.Top);
        //         }
        //         // Realistically we also don't want to update the start position when moving from one docked state to another (or to and from maximized),
        //         // but it's tricky to detect and this is already a workaround for a bug that's fixed in newer versions of the framework.
        //         // Not going to try to handle all cases.
        //     }
        //
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // private IntPtr _HandleExitSizeMove(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // This is only intercepted to deal with bugs in Window in .Net 3.5 and below.
        //     Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
        //
        //     _isUserResizing = false;
        //
        //     // On Win7 the user can change the Window's state by dragging the window to the top of the monitor.
        //     // If they did that, then we need to try to update the restore bounds or else WPF will put the window at the maximized location (e.g. (-8,-8)).
        //     if (_window.WindowState == WindowState.Maximized)
        //     {
        //         Assert.IsTrue(Utility.IsOSWindows7OrNewer);
        //         _window.Top = _windowPosAtStartOfUserMove.Y;
        //         _window.Left = _windowPosAtStartOfUserMove.X;
        //     }
        //
        //     handled = false;
        //     return IntPtr.Zero;
        // }
        //
        // private IntPtr _HandleMove(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
        // {
        //     // This is only intercepted to deal with bugs in Window in .Net 3.5 and below.
        //     Assert.IsTrue(Utility.IsPresentationFrameworkVersionLessThan4);
        //
        //     if (_isUserResizing)
        //     {
        //         _hasUserMovedWindow = true;
        //     }
        //
        //     handled = false;
        //     return IntPtr.Zero;
        // }

        #endregion

        /// <summary>Add and remove a native WindowStyle from the HWND.</summary>
        /// <param name="removeStyle">The styles to be removed.  These can be bitwise combined.</param>
        /// <param name="addStyle">The styles to be added.  These can be bitwise combined.</param>
        /// <returns>Whether the styles of the HWND were modified as a result of this call.</returns>
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private bool _ModifyStyle(WS removeStyle, WS addStyle)
        {
            Assert.IsNotDefault(_hwnd);
            var dwStyle = (WS)NativeMethods.GetWindowLongPtr(_hwnd, GWL.STYLE).ToInt32();
            var dwNewStyle = (dwStyle & ~removeStyle) | addStyle;
            if (dwStyle == dwNewStyle)
            {
                return false;
            }

            NativeMethods.SetWindowLongPtr(_hwnd, GWL.STYLE, new IntPtr((int)dwNewStyle));
            return true;
        }

        /// <summary>
        /// Get the WindowState as the native HWND knows it to be.  This isn't necessarily the same as what Window thinks.
        /// </summary>
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private WindowState _GetHwndState()
        {
            var wpl = NativeMethods.GetWindowPlacement(_hwnd);
            switch (wpl.showCmd)
            {
                case SW.SHOWMINIMIZED: return WindowState.Minimized;
                case SW.SHOWMAXIMIZED: return WindowState.Maximized;
            }
            return WindowState.Normal;
        }

        /// <summary>
        /// Get the bounding rectangle for the window in physical coordinates.
        /// </summary>
        /// <returns>The bounding rectangle for the window.</returns>
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private Rect _GetWindowRect()
        {
            // Get the window rectangle.
            RECT windowPosition = NativeMethods.GetWindowRect(_hwnd);
            return new Rect(windowPosition.Left, windowPosition.Top, windowPosition.Width, windowPosition.Height);
        }

        /// <summary>
        /// Update the items in the system menu based on the current, or assumed, WindowState.
        /// </summary>
        /// <param name="assumeState">
        /// The state to assume that the Window is in.  This can be null to query the Window's state.
        /// </param>
        /// <remarks>
        /// We want to update the menu while we have some control over whether the caption will be repainted.
        /// </remarks>
        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _UpdateSystemMenu(WindowState? assumeState)
        {
            const MF mfEnabled = MF.ENABLED | MF.BYCOMMAND;
            const MF mfDisabled = MF.GRAYED | MF.DISABLED | MF.BYCOMMAND;

            WindowState state = assumeState ?? _GetHwndState();

            if (null != assumeState || _lastMenuState != state)
            {
                _lastMenuState = state;

                bool modified = _ModifyStyle(WS.VISIBLE, 0);
                IntPtr hmenu = NativeMethods.GetSystemMenu(_hwnd, false);
                if (IntPtr.Zero != hmenu)
                {
                    var dwStyle = (WS)NativeMethods.GetWindowLongPtr(_hwnd, GWL.STYLE).ToInt32();

                    bool canMinimize = Utility.IsFlagSet((int)dwStyle, (int)WS.MINIMIZEBOX);
                    bool canMaximize = Utility.IsFlagSet((int)dwStyle, (int)WS.MAXIMIZEBOX);
                    bool canSize = Utility.IsFlagSet((int)dwStyle, (int)WS.THICKFRAME);

                    switch (state)
                    {
                        case WindowState.Maximized:
                            NativeMethods.EnableMenuItem(hmenu, SC.RESTORE, mfEnabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MOVE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.SIZE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MINIMIZE, canMinimize ? mfEnabled : mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MAXIMIZE, mfDisabled);
                            break;
                        case WindowState.Minimized:
                            NativeMethods.EnableMenuItem(hmenu, SC.RESTORE, mfEnabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MOVE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.SIZE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MINIMIZE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MAXIMIZE, canMaximize ? mfEnabled : mfDisabled);
                            break;
                        default:
                            NativeMethods.EnableMenuItem(hmenu, SC.RESTORE, mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MOVE, mfEnabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.SIZE, canSize ? mfEnabled : mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MINIMIZE, canMinimize ? mfEnabled : mfDisabled);
                            NativeMethods.EnableMenuItem(hmenu, SC.MAXIMIZE, canMaximize ? mfEnabled : mfDisabled);
                            break;
                    }
                }

                if (modified)
                {
                    _ModifyStyle(0, WS.VISIBLE);
                }
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _UpdateFrameState(bool force)
        {
            if (IntPtr.Zero == _hwnd || _hwndSource.IsDisposed)
            {
                return;
            }

            // Don't rely on SystemParameters for this, just make the check ourselves.
            bool frameState = NativeMethods.DwmIsCompositionEnabled();

            if (force || frameState != _isGlassEnabled)
            {
                _isGlassEnabled = frameState && ChromeFixInfo.GlassFrameThickness != default(Thickness);

                if (!_isGlassEnabled)
                {
                    _SetRoundingRegion(null);
                }
                else
                {
                    _ClearRoundingRegion();
                    _ExtendGlassFrame();
                }

                // NativeMethods.SetWindowPos(_hwnd, IntPtr.Zero, 0, 0, 0, 0, _SwpFlags);
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _ClearRoundingRegion()
        {
            NativeMethods.SetWindowRgn(_hwnd, IntPtr.Zero, NativeMethods.IsWindowVisible(_hwnd));
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _SetRoundingRegion(WINDOWPOS? wp)
        {
            const int MONITOR_DEFAULTTONEAREST = 0x00000002;

            // We're early - WPF hasn't necessarily updated the state of the window.
            // Need to query it ourselves.
            WINDOWPLACEMENT wpl = NativeMethods.GetWindowPlacement(_hwnd);

            if (wpl.showCmd == SW.SHOWMAXIMIZED)
            {
                int left;
                int top;

                if (wp.HasValue)
                {
                    left = wp.Value.x;
                    top = wp.Value.y;
                }
                else
                {
                    Rect r = _GetWindowRect();
                    left = (int)r.Left;
                    top = (int)r.Top;
                }

                IntPtr hMon = NativeMethods.MonitorFromWindow(_hwnd, MONITOR_DEFAULTTONEAREST);

                MONITORINFO mi = NativeMethods.GetMonitorInfo(hMon);
                RECT rcMax = mi.rcWork;
                // The location of maximized window takes into account the border that Windows was
                // going to remove, so we also need to consider it.
                rcMax.Offset(-left, -top);

                IntPtr hrgn = IntPtr.Zero;
                try
                {
                    hrgn = NativeMethods.CreateRectRgnIndirect(rcMax);
                    NativeMethods.SetWindowRgn(_hwnd, hrgn, NativeMethods.IsWindowVisible(_hwnd));
                    hrgn = IntPtr.Zero;
                }
                finally
                {
                    Utility.SafeDeleteObject(ref hrgn);
                }
            }
            else
            {
                Size windowSize;

                // Use the size if it's specified.
                if (null != wp && !Utility.IsFlagSet(wp.Value.flags, (int)SWP.NOSIZE))
                {
                    windowSize = new Size((double)wp.Value.cx, (double)wp.Value.cy);
                }
                else if (null != wp && (_lastRoundingState == _window.WindowState))
                {
                    return;
                }
                else
                {
                    windowSize = _GetWindowRect().Size;
                }

                _lastRoundingState = _window.WindowState;

                IntPtr hrgn = IntPtr.Zero;
                try
                {
                    // DpiScale dpi = _window.GetDpi();
                    DpiScale dpi = GetDpi(_window);

                    double shortestDimension = Math.Min(windowSize.Width, windowSize.Height);

                    double topLeftRadius = DpiHelper.LogicalPixelsToDevice(new Point(ChromeFixInfo.CornerRadius.TopLeft, 0), dpi.DpiScaleX, dpi.DpiScaleY).X;
                    topLeftRadius = Math.Min(topLeftRadius, shortestDimension / 2);

                    if (_IsUniform(ChromeFixInfo.CornerRadius))
                    {
                        // RoundedRect HRGNs require an additional pixel of padding.
                        hrgn = _CreateRoundRectRgn(new Rect(windowSize), topLeftRadius);
                    }
                    else
                    {
                        // We need to combine HRGNs for each of the corners.
                        // Create one for each quadrant, but let it overlap into the two adjacent ones
                        // by the radius amount to ensure that there aren't corners etched into the middle
                        // of the window.
                        hrgn = _CreateRoundRectRgn(new Rect(0, 0, windowSize.Width / 2 + topLeftRadius, windowSize.Height / 2 + topLeftRadius), topLeftRadius);

                        double topRightRadius = DpiHelper.LogicalPixelsToDevice(new Point(ChromeFixInfo.CornerRadius.TopRight, 0), dpi.DpiScaleX, dpi.DpiScaleY).X;
                        topRightRadius = Math.Min(topRightRadius, shortestDimension / 2);
                        Rect topRightRegionRect = new Rect(0, 0, windowSize.Width / 2 + topRightRadius, windowSize.Height / 2 + topRightRadius);
                        topRightRegionRect.Offset(windowSize.Width / 2 - topRightRadius, 0);
                        Assert.AreEqual(topRightRegionRect.Right, windowSize.Width);

                        _CreateAndCombineRoundRectRgn(hrgn, topRightRegionRect, topRightRadius);

                        double bottomLeftRadius = DpiHelper.LogicalPixelsToDevice(new Point(ChromeFixInfo.CornerRadius.BottomLeft, 0), dpi.DpiScaleX, dpi.DpiScaleY).X;
                        bottomLeftRadius = Math.Min(bottomLeftRadius, shortestDimension / 2);
                        Rect bottomLeftRegionRect = new Rect(0, 0, windowSize.Width / 2 + bottomLeftRadius, windowSize.Height / 2 + bottomLeftRadius);
                        bottomLeftRegionRect.Offset(0, windowSize.Height / 2 - bottomLeftRadius);
                        Assert.AreEqual(bottomLeftRegionRect.Bottom, windowSize.Height);

                        _CreateAndCombineRoundRectRgn(hrgn, bottomLeftRegionRect, bottomLeftRadius);

                        double bottomRightRadius = DpiHelper.LogicalPixelsToDevice(new Point(ChromeFixInfo.CornerRadius.BottomRight, 0), dpi.DpiScaleX, dpi.DpiScaleY).X;
                        bottomRightRadius = Math.Min(bottomRightRadius, shortestDimension / 2);
                        Rect bottomRightRegionRect = new Rect(0, 0, windowSize.Width / 2 + bottomRightRadius, windowSize.Height / 2 + bottomRightRadius);
                        bottomRightRegionRect.Offset(windowSize.Width / 2 - bottomRightRadius, windowSize.Height / 2 - bottomRightRadius);
                        Assert.AreEqual(bottomRightRegionRect.Right, windowSize.Width);
                        Assert.AreEqual(bottomRightRegionRect.Bottom, windowSize.Height);

                        _CreateAndCombineRoundRectRgn(hrgn, bottomRightRegionRect, bottomRightRadius);
                    }

                    NativeMethods.SetWindowRgn(_hwnd, hrgn, NativeMethods.IsWindowVisible(_hwnd));
                    hrgn = IntPtr.Zero;
                }
                finally
                {
                    // Free the memory associated with the HRGN if it wasn't assigned to the HWND.
                    Utility.SafeDeleteObject(ref hrgn);
                }
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private static IntPtr _CreateRoundRectRgn(Rect region, double radius)
        {
            // Round outwards.

            if (DoubleUtilities.AreClose(0, radius))
            {
                return NativeMethods.CreateRectRgn(
                    (int)Math.Floor(region.Left),
                    (int)Math.Floor(region.Top),
                    (int)Math.Ceiling(region.Right),
                    (int)Math.Ceiling(region.Bottom));
            }

            // RoundedRect HRGNs require an additional pixel of padding on the bottom right to look correct.
            return NativeMethods.CreateRoundRectRgn(
                (int)Math.Floor(region.Left),
                (int)Math.Floor(region.Top),
                (int)Math.Ceiling(region.Right) + 1,
                (int)Math.Ceiling(region.Bottom) + 1,
                (int)Math.Ceiling(radius),
                (int)Math.Ceiling(radius));
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "HRGNs")]
        private static void _CreateAndCombineRoundRectRgn(IntPtr hrgnSource, Rect region, double radius)
        {
            IntPtr hrgn = IntPtr.Zero;
            try
            {
                hrgn = _CreateRoundRectRgn(region, radius);
                CombineRgnResult result = NativeMethods.CombineRgn(hrgnSource, hrgnSource, hrgn, RGN.OR);
                if (result == CombineRgnResult.ERROR)
                {
                    throw new InvalidOperationException("Unable to combine two HRGNs.");
                }
            }
            catch
            {
                Utility.SafeDeleteObject(ref hrgn);
                throw;
            }
        }

        private static bool _IsUniform(CornerRadius cornerRadius)
        {
            if (!DoubleUtilities.AreClose(cornerRadius.BottomLeft, cornerRadius.BottomRight))
            {
                return false;
            }

            if (!DoubleUtilities.AreClose(cornerRadius.TopLeft, cornerRadius.TopRight))
            {
                return false;
            }

            if (!DoubleUtilities.AreClose(cornerRadius.BottomLeft, cornerRadius.TopRight))
            {
                return false;
            }

            return true;
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _ExtendGlassFrame()
        {
            Assert.IsNotNull(_window);

            // Expect that this might be called on OSes other than Vista.
            if (!Utility.IsOSVistaOrNewer)
            {
                // Not an error.  Just not on Vista so we're not going to get glass.
                return;
            }

            if (IntPtr.Zero == _hwnd)
            {
                // Can't do anything with this call until the Window has been shown.
                return;
            }

            // Ensure standard HWND background painting when DWM isn't enabled.
            if (!NativeMethods.DwmIsCompositionEnabled())
            {
                _hwndSource.CompositionTarget.BackgroundColor = SystemColors.WindowColor;
            }
            else
            {
                // DpiScale dpi = _window.GetDpi();
                DpiScale dpi = GetDpi(_window);

                // This makes the glass visible at a Win32 level so long as nothing else is covering it.
                // The Window's Background needs to be changed independent of this.

                // Apply the transparent background to the HWND
                // _hwndSource.CompositionTarget.BackgroundColor = Colors.Transparent;

                // Thickness is going to be DIPs, need to convert to system coordinates.
                Thickness deviceGlassThickness = DpiHelper.LogicalThicknessToDevice(ChromeFixInfo.GlassFrameThickness, dpi.DpiScaleX, dpi.DpiScaleY);

                if (ChromeFixInfo.NonClientFrameEdges != NonClientFrameEdges.None)
                {
                    Thickness windowResizeBorderThicknessDevice = DpiHelper.LogicalThicknessToDevice(SystemParameters.WindowResizeBorderThickness, dpi.DpiScaleX, dpi.DpiScaleY);

                    if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Top))
                    {
                        deviceGlassThickness.Top -= windowResizeBorderThicknessDevice.Top;
                        deviceGlassThickness.Top = Math.Max(0, deviceGlassThickness.Top);
                    }
                    if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Left))
                    {
                        deviceGlassThickness.Left -= windowResizeBorderThicknessDevice.Left;
                        deviceGlassThickness.Left = Math.Max(0, deviceGlassThickness.Left);
                    }
                    if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Bottom))
                    {
                        deviceGlassThickness.Bottom -= windowResizeBorderThicknessDevice.Bottom;
                        deviceGlassThickness.Bottom = Math.Max(0, deviceGlassThickness.Bottom);
                    }
                    if (Utility.IsFlagSet((int)ChromeFixInfo.NonClientFrameEdges, (int)NonClientFrameEdges.Right))
                    {
                        deviceGlassThickness.Right -= windowResizeBorderThicknessDevice.Right;
                        deviceGlassThickness.Right = Math.Max(0, deviceGlassThickness.Right);
                    }
                }

                var dwmMargin = new MARGINS
                {
                    // err on the side of pushing in glass an extra pixel.
                    cxLeftWidth = (int)Math.Ceiling(deviceGlassThickness.Left),
                    cxRightWidth = (int)Math.Ceiling(deviceGlassThickness.Right),
                    cyTopHeight = (int)Math.Ceiling(deviceGlassThickness.Top),
                    cyBottomHeight = (int)Math.Ceiling(deviceGlassThickness.Bottom),
                };

                NativeMethods.DwmExtendFrameIntoClientArea(_hwnd, ref dwmMargin);
            }
        }

        /// <summary>
        /// Matrix of the HT values to return when responding to NC window messages.
        /// </summary>
        [SuppressMessage("Microsoft.Performance", "CA1814:PreferJaggedArraysOverMultidimensional", MessageId = "Member")]
        private static readonly HT[,] _HitTestBorders = new[,]
        {
            { HT.TOPLEFT,    HT.TOP,     HT.TOPRIGHT    },
            { HT.LEFT,       HT.CLIENT,  HT.RIGHT       },
            { HT.BOTTOMLEFT, HT.BOTTOM,  HT.BOTTOMRIGHT },
        };
        
        private HT _HitTestNca(Rect windowPosition, Point mousePosition)
        {
            // Determine if hit test is for resizing, default middle (1,1).
            int uRow = 1;
            int uCol = 1;
            bool onResizeBorder = false;
        
            // Determine if the point is at the top or bottom of the window.
            if (mousePosition.Y >= windowPosition.Top && mousePosition.Y < windowPosition.Top + ChromeFixInfo.ResizeBorderThickness.Top + ChromeFixInfo.CaptionHeight)
            {
                onResizeBorder = (mousePosition.Y < (windowPosition.Top + ChromeFixInfo.ResizeBorderThickness.Top));
                uRow = 0; // top (caption or resize border)
            }
            else if (mousePosition.Y < windowPosition.Bottom && mousePosition.Y >= windowPosition.Bottom - (int)ChromeFixInfo.ResizeBorderThickness.Bottom)
            {
                uRow = 2; // bottom
            }
        
            // Determine if the point is at the left or right of the window.
            if (mousePosition.X >= windowPosition.Left && mousePosition.X < windowPosition.Left + (int)ChromeFixInfo.ResizeBorderThickness.Left)
            {
                uCol = 0; // left side
            }
            else if (mousePosition.X < windowPosition.Right && mousePosition.X >= windowPosition.Right - ChromeFixInfo.ResizeBorderThickness.Right)
            {
                uCol = 2; // right side
            }
        
            // If the cursor is in one of the top edges by the caption bar, but below the top resize border,
            // then resize left-right rather than diagonally.
            if (uRow == 0 && uCol != 1 && !onResizeBorder)
            {
                uRow = 1;
            }
        
            HT ht = _HitTestBorders[uRow, uCol];
        
            if (ht == HT.TOP && !onResizeBorder)
            {
                ht = HT.CAPTION;
            }
        
            return ht;
        }

        #region Remove Custom Chrome Methods

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _RestoreStandardChromeState(bool isClosing)
        {
            VerifyAccess();

            _UnhookCustomChrome();

            if (!isClosing && !_hwndSource.IsDisposed)
            {
                _RestoreFrameworkIssueFixups();
                _RestoreGlassFrame();
                _RestoreHrgn();

                _window.InvalidateMeasure();
            }
        }

        /// <SecurityNote>
        ///   Critical : Unsubscribes event handler from critical _hwndSource
        /// <SecurityNote>
        [SecurityCritical]
        private void _UnhookCustomChrome()
        {
            Assert.IsNotDefault(_hwnd);
            Assert.IsNotNull(_window);

            if (_isHooked)
            {
                _hwndSource.RemoveHook(_WndProc);
                _isHooked = false;
            }
        }

        /// <SecurityNote>
        ///   Critical : Unsubscribes critical event handler
        /// <SecurityNote>
        [SecurityCritical]
        private void _RestoreFrameworkIssueFixups()
        {
            var rootElement = (FrameworkElement)VisualTreeHelper.GetChild(_window, 0);

            // Undo anything that was done before.
            rootElement.Margin = new Thickness();

            // This margin is only necessary if the client rect is going to be calculated incorrectly by WPF.
            // This bug was fixed in V4 of the framework.
            if (Utility.IsPresentationFrameworkVersionLessThan4)
            {
                Assert.IsTrue(_isFixedUp);
                _window.StateChanged -= _FixupRestoreBounds;
                _isFixedUp = false;
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _RestoreGlassFrame()
        {
            Assert.IsNull(ChromeFixInfo);
            Assert.IsNotNull(_window);

            // Expect that this might be called on OSes other than Vista
            // and if the window hasn't yet been shown, then we don't need to undo anything.
            if (!Utility.IsOSVistaOrNewer || _hwnd == IntPtr.Zero)
            {
                return;
            }

            _hwndSource.CompositionTarget.BackgroundColor = SystemColors.WindowColor;

            if (NativeMethods.DwmIsCompositionEnabled())
            {
                // If glass is enabled, push it back to the normal bounds.
                var dwmMargin = new MARGINS();
                NativeMethods.DwmExtendFrameIntoClientArea(_hwnd, ref dwmMargin);
            }
        }

        /// <SecurityNote>
        ///   Critical : Calls critical methods
        /// <SecurityNote>
        [SecurityCritical]
        private void _RestoreHrgn()
        {
            _ClearRoundingRegion();
            NativeMethods.SetWindowPos(_hwnd, IntPtr.Zero, 0, 0, 0, 0, _SwpFlags);
        }

        #endregion
    }
}
